Video display controllers for personal computers convert data from a main central processing unit to pixel elements for display on e.g. cathode ray tube. Such subsystems typically involve use of a VRAM for storage of pixel data for the display, a graphics controller, a colour lookup table and a digital-to-analog converter for converting the digital display signals into analog signals which can be displayed by the cathode ray tube.
In order to reduce the cost of such systems, it has been an objective to create a video controller on a single chip. However this has increased the number of pins through which data must be transferred into and out of the video controller, which is costly.
In order to reduce the number of pins which must be serviced by the internal controller, in one design parts of the video controller have been moved off the chip. While this achieved the objective of reducing the pin count, it required the use of a separate chip containing logic for interfacing the VRAM display memory, and increased the parts count and thus the cost due to the inability to integrate the entire video controller on a single chip.